Abstract
The intracytoplasmic origin of the flagella in Euglena gracilis is described with particular regard to the transitional zone. Our observations are compared with those reported for Entosiphon. The structure of the paraflagellar body has been studied by diphractometric analysis. The PFB of Euglena may be described as a crystal with a monoclinic or slightly distorted hexagonal unit cell with dimensions: a = 8.9 nm; b = 7.7 nm; c = 8.3 nm; 0 = 110°.